1. Field of the Invention
The present invention relates to an apparatus and method for anchoring surgical suture to bone. More specifically, the present invention relates to arthroscopic apparatus and methods for anchoring suture to cancellous bone using a suture anchor having an auger-like configuration.
2. Description of the Related Art
When soft tissue tears away from bone, reattachment becomes necessary. Various devices, including sutures alone, screws, staples, wedges, and plugs have been used to secure soft tissue to bone. Recently, various types of threaded suture anchors have been developed for this purpose.
Suture anchors have been developed that are designed to be inserted into a pre-drilled hole. Other suture anchors are self-tapping. Self-tapping screws are shown, for example, in U.S. Pat. No. 4,632,100, which discloses a cylindrical suture anchor. The suture anchor of the '100 patent includes a drill bit at a leading end for boring a hole in a bone, followed by a flight of threads spaced from the drill bit for securing the anchor into the hole created by the drill bit. U.S. Pat. No. 5,370,662 discloses a self-tapping suture anchor having a flight of threads around a solid body. U.S. Pat. No. 5,156,616 discloses a similar suture anchor having an axial opening for holding a knotted piece of suture.
All of the above-noted suture anchors rely on a flight of threads disposed on the outer surface of a shank to secure the anchor to the bone. They all provide a relatively easy method of suture fixation in hard, cortical bone.
Recent studies indicate, however, that the above-noted suture anchors may have problems related to inadequate "pull-out" strength. This is true especially in softer bone sites, such as cancellous bone, or in bone tissue that has become compromised, such as in osteoporotic bone sites. The structure of cancellous, or cancellated, bone is lattice-like, or spongy. Osteoporotic bone is the result of a condition that reduces the quantity of bone or atrophies skeletal tissue, causing a porous condition of the bones. These bone types may present a limited range of specific fixation points that are available to the surgeon.
Also, certain known suture anchors also have a tendency to "back out" of the implantation site. Moreover, substantial bone loss is incurred simply upon installation of the above-described prior art suture anchors. This problem is acute particularly during procedures that require removal or relocation of suture anchors.
Accordingly, a need exists for a suture anchor that can be secured easily and effectively, especially in softer types of bone. A need also exists for a suture anchor that displaces a minimum amount of bone upon insertion. In addition, a need exists for a suture anchor having exceptional pull-out strength, especially in soft bone. A need also exists for a suture anchor that is averse to "backing out" of the insertion site.